Tray sealer

ABSTRACT

A tray sealer that includes a control unit and a sealing station is presented. The sealing station comprises a tool upper part, a clamping frame and a tool lower part. The interior of the tool upper part comprises a dome-shaped die for deforming a top film. The dome-shaped die comprises at least a first channel and the tool upper part comprises a second channel. The dome-shaped die may have an inner contact surface. The clamping frame may clamp the top film in position on the tool upper part in a gas-tight manner so as to define an upper chamber within the tool upper part. In one embodiment, a vacuum sensor is operably connected to the control unit and is disposed between the dome-shaped die and a vacuum generator. The control unit may detect a tear in the film using a pressure profile generated by the vacuum sensor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application claims priority to European Patent Application No. 17 174 272.9, filed on Jun. 2, 2017, to Luciano Capriotti and Patrick Jung, currently pending, the entire disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a tray sealer for thermoforming a skinnable top film and detecting defective packages.

BACKGROUND OF THE INVENTION

WO 2015091404 A1 discloses a tray sealer for sealing a tray with a skinnable top film. The top film is here heated using a dome-shaped plate, which is adapted to be moved relative to a dome-shaped die, and is pulled by the dome-shaped plate itself into the dome-shaped die for the purpose of forming. The movable and heatable dome-shaped plate involves a high constructional outlay.

EP 2815983 A1 discloses a tray sealer, which, in a similar manner, is configured for heating a skinnable top film by applying it to a heated interior wall of a dome-shaped die. In a first step, heated air is here guided via the sealing tool through the dome-shaped die and onto the top film and, subsequently, this air is extracted via the common ducts from the space between the sealing tool upper part and the preheated top film. This process combination of overpressure and evacuation is disadvantageous as regards the period of time needed until the thermoforming process ends in the dome-shaped die.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide an improved tray sealer for sealing a tray with a skinnable top film.

The tray sealer according to the present invention includes a control unit and a sealing station, which comprises a tool upper part, a clamping frame and a tool lower part, wherein the interior of the tool upper part has arranged therein a dome-shaped die for deforming a skinnable top film, preferably a top film having a thickness of less than 200 μm. The dome-shaped die comprises at least a first channel, the tool upper part comprises a second channel and the dome-shaped die has an inner contact surface. The clamping frame may be configured to clamp the top film in position on the tool upper part in a gas-tight manner so as to define an upper chamber within the tool upper part. One embodiment of the invention may be the inclusion of a vacuum sensor (pressure sensor), which is connected to the control unit, may be provided between the dome-shaped die and a vacuum generator, the control unit being configured to detect a tear in the film on the basis of the pressure profile (viz. pressure curve). For example, the top film can be thermoformed into the dome-shaped die and a possible tear in the film caused during the thermoforming process would be detected. To this end, a pressure profile ascertained using the vacuum sensor may be compared with a predetermined pressure profile or a pressure profile to be expected. If the pressure profile ascertained should deviate from the predetermined pressure profile and if the deviation should exceed a predetermined tolerance, the control unit will interpret this as an indication of a tear in the film. The deviation may be measured during the entire thermoforming process. The deviation may occur in the form of a pressure increase or an insufficient gradient of the evacuation curve and may be caused by a tear in the film. It is also imaginable that a predetermined final vacuum value is not accomplished due to a tear in the film and that this may be considered to be an indication of a tear in the film.

Such a tear in the film may be primarily caused by an unequal temperature distribution in the skin film, since, due to the radiant heat of the sealing surface, the skin film may be heated more intensively in this area than in other areas. In particular when the skin film comes into contact with the sealing surface during the thermoforming process, this may have a negative effect and result in film tearing. Likewise, an already pre-damaged film would be detected during the thermoforming process. Hence, a production of defective packages, which would have to be removed later on, will be prevented, or situations will be prevented, in which the process cannot be duly finished, since, due to leakiness of the top film prior to skinning, a final vacuum cannot be accomplished or can only be accomplished after a long period of time. In one embodiment, it is also imaginable to advance the partially deformed top film and to execute a new thermoforming process with a new film section.

Preferably, the dome-shaped die comprises a plurality of venting ducts for thermoforming the top film uniformly and quickly into the interior of the dome-shaped die. The venting ducts can also be used for supplying air to the sealing tool, so as to allow the top film to move downwards into contact with the product and the inner sides as well as to a position of contact with the tray edge.

Preferably, the dome-shaped die has a sealing surface for sealing the top film onto the tray edge of the tray using pressure and heat.

According to an advantageous embodiment, the dome-shaped die may be movable between an upper position for deforming the skinnable top film and a lower position for sealing the top film onto the tray edge of at least one tray.

Preferably, a seal may be provided at a transition of the first channel from the dome-shaped die to the second channel of the tool upper part, so that the chamber can be evacuated. The seal may also be provided in the event that the top film may be in contact with the lower side of the dome-shaped die and divides the chamber into two areas. A subchamber may be located between the top film and the sealing tool, but outside the dome-shaped die, and a second subchamber may be defined by the interior of the dome-shaped die and the top film.

The method according to the present invention, which may be used for operating a tray sealer including a control unit as well as a sealing station comprising a tool upper part, a clamping frame and a tool lower part, wherein the tool upper part receives therein a dome-shaped die for deforming a skinnable top film, wherein the dome-shaped die comprises at least a first channel, wherein the tool upper part comprises a second channel, wherein the dome-shaped die has an inner contact surface, and wherein the clamping frame may be configured to clamp the top film in position on the tool upper part in a gas-tight manner so as to define a chamber within the tool upper part, is wherein, using a vacuum sensor provided between the dome-shaped die and a vacuum generator, a negative pressure is measured, and that the control unit detects a tear in the film on the basis of the pressure profile (viz. pressure curve).

Preferably, in one embodiment, the control unit will show a message on a display, when a tear in the film is detected. In this way, the operator is informed of the reason for the interruption of the process and can, if necessary, adapt parameters for the next new thermoforming process so as to avoid further film tearing.

Preferably, in one embodiment, the control unit will not start or will discontinue a sealing process when a tear in the film is detected, since the packages in question are at least partially defective and thus useless.

According to a preferred embodiment, air will be supplied to the tool upper part and the top film will be advanced in the conveying direction, when a tear in the film is detected, so as thermoform, in a further attempt, a subsequent new film section into the dome-shaped die. In this connection, it is imaginable to discontinue the packaging process after film tearing has occurred three times in succession, so as to adapt process parameters or search for other causes of error.

Optionally, the pressure profile may be used as a basis for detecting that the top film is in contact with the inner contact surface of the dome-shaped die, whereupon the next process step may be started or initiated. Time settings with the usual additional safety buffers are thus no longer necessary.

Other aspects and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments and the accompanying drawing figures.

DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

In the following, an advantageous embodiment of the present invention will be explained in more detail making reference to a drawing, in which the individual figures show:

FIG. 1 is a perspective view of one embodiment of a tray sealer in accordance with the teachings of the present disclosure;

FIG. 2 is a sectional view of one embodiment of a sealing station in accordance with the teachings of the present disclosure shown in an open position;

FIG. 3 is a sectional view of the sealing station of FIG. 2 shown during the thermoforming process; and

FIG. 4 is the sectional view of the sealing station of FIG. 2 showing a thermoformed top film.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described with reference to the drawing figures, in which like reference numerals refer to like parts throughout. For purposes of clarity in illustrating the characteristics of the present invention, proportional relationships of the elements have not necessarily been maintained in the drawing figures.

The following detailed description of the invention references specific embodiments in which the invention can be practiced. The embodiments are intended to describe aspects of the invention in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments can be utilized and changes can be made without departing from the scope of the present invention. The present invention is defined by the appended claims and the description is, therefore, not to be taken in a limiting sense and shall not limit the scope of equivalents to which such claims are entitled.

FIG. 1 shows a tray sealer 1 comprising a sealing station 2, which seals trays 100 with a top film 3, and a gripper system 4, which moves the trays 100 in a conveying direction P from a feed conveyor 5 into the sealing station 2. The sealing station 2 has a tool lower part 6 and a tool upper part 7 arranged above the latter. A control unit 8 controls and monitors all the processes in the tray sealer 1. The sealing station 2 is provided for sealing a plurality of trays 100. This may take place in the form of multi-row sealing and/or multi-track sealing, multi-row meaning that a plurality of trays 100 are provided in succession in the conveying direction P and multi-track meaning that there are provided two or more tracks of trays 100, which, when seen in the conveying direction P, are arranged side by side in parallel.

FIG. 2 shows a sealing station 2 according to the present invention at an open position, at which the tool lower part 6 is spaced apart from the tool upper part 7 and the top film 3 extends therebetween in the conveying direction P. The tool lower part 6 comprises a tray accommodation unit 9 and is connected via a vacuum line 11 and a first valve 12 to a vacuum generator 10, for example, a central vacuum unit or a vacuum pump, so as to allow the package interior to be evacuated prior to closing. A clamping frame 13 is provided between the tool lower part 6 and the tool upper part 7, so as to clamp the top film 3 against the tool upper part 7 along the outer circumference of the latter in a gas- and pressure-tight manner, thus defining a chamber 14 between the top film 3 and the tool upper part 7.

The bell-shaped tool upper part 7 receives in the interior thereof a dome-shaped die 15 and a pressure plate 16, the pressure plate 16 having arranged thereon a cutting device 17 for cutting the top film 3 outside the dome-shaped die 15 along a tray edge 101 of the tray 100 around the circumference of the latter. In the tray 100 a product 102 is shown, which projects upwards beyond the tray edge 101. Also products 102, which do not project beyond the tray edge 101 are imaginable.

The dome-shaped die 15 has a first channel 19, which can be brought into fluid communication with a second channel 20 that penetrates the wall of the bell-shaped tool upper part 7. Via the two channels 19, 20, air may be supplied to the chamber 14 or removed therefrom. The channel 19 may be configured as a tube and extend through the pressure plate 16 up to or into the tool upper part 7 while the dome-shaped die 15 occupies its upper position. The dome-shaped die 15 itself comprises ducts 21 through which a vacuum can be generated between the dome-shaped die 15 and the top film 3, and, for the actual skinning process, where the top film 3 is moved to a skin-like position of close contact with the product 102, air can flow from the first channel 19 through the dome-shaped die 15 into the chamber 14.

FIG. 3 shows the sealing station 2, in the case of which the clamping frame 13 clamps the top film 3 upwards onto the sealing tool upper part 7 along the circumference of the latter in a gas-tight manner. At this upper position of the dome-shaped die 15, the first channel 19 in the tool upper part 7 is connected to the second channel 20 using a seal 23. The second channel 20, in turn, is connected to a second valve 25 via a line 24. At the second valve 25, a vacuum generator 26, for example a central vacuum unit or a vacuum pump, is provided for thermoforming the skinnable top film 3 into an inner area of the dome-shaped die 15 when a negative pressure is applied via the line 24. Via the venting ducts 21 air is extracted in the direction of the arrows.

During the process in the course of which the top film 3 is thermoformed onto the inner sides of the dome-shaped die 15 using the negative pressure generated by the vacuum generator 26 between the top film 3 and the interior of the dome-shaped die 15, there is the risk that the top film 3 will tear. A vacuum sensor 27 provided in line 24 or in the second channel 20 transmits its measurement values to the control unit 8, which monitors and evaluates the pressure profile. If the intended pressure profile should fail to reach a target value to be expected within a predetermined time or should exhibit a pressure increase or a change of pressure deviating from a theoretical pressure profile, this behavior will be interpreted as an indication of a tear in the film and the evacuation process will be discontinued and a message shown on a display 28. The vacuum sensor (pressure sensor) 27 is preferably configured for a measurement range of 0 to 1 bar.

FIG. 4 shows the thermoformed top film 3 which is in contact with inner contact surfaces 15 a of the dome-shaped die 15. Through the heating elements 22 in the dome-shaped die 15, the top film 3 is heated to a temperature, which is required for the subsequent skinning process.

For sealing the top film 3 onto the tray edge 101 during a subsequent sealing process, the dome-shaped die 15 has, on the lower side thereof, a circumferentially extending sealing surface 15 b, which is configured such that it is congruent with the tray edge 101.

From the foregoing, it will be seen that this invention is one well adapted to attain all the ends and objects hereinabove set forth together with other advantages which are obvious and which are inherent to the structure. It will be understood that certain features and sub combinations are of utility and may be employed without reference to other features and sub combinations. This is contemplated by and is within the scope of the claims. Since many possible embodiments of the invention may be made without departing from the scope thereof, it is also to be understood that all matters herein set forth or shown in the accompanying drawings are to be interpreted as illustrative and not limiting.

The constructions and methods described above and illustrated in the drawings are presented by way of example only and are not intended to limit the concepts and principles of the present invention. Thus, there has been shown and described several embodiments of a novel invention.

As is evident from the foregoing description, certain aspects of the present invention are not limited by the particular details of the examples illustrated herein, and it is therefore contemplated that other modifications and applications, or equivalents thereof, will occur to those skilled in the art. The terms “having” and “including” and similar terms as used in the foregoing specification are used in the sense of “optional” or “may include” and not as “required”. Many changes, modifications, variations and other uses and applications of the present construction will, however, become apparent to those skilled in the art after considering the specification and the accompanying drawings. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention which is limited only by the claims which follow. 

What is claimed is:
 1. A tray sealer including a control unit and a sealing station, the tray sealer comprises: a tool upper part; a clamping frame; and a tool lower part; wherein the interior of the tool upper part has arranged therein a dome-shaped die for deforming a top film; wherein the dome-shaped die comprises at least a first channel, and the tool upper part comprises a second channel; wherein the dome-shaped die has an inner contact surface; and wherein the clamping frame is disposed to clamp the top film in position on the tool upper part in a gas-tight manner so as to define an upper chamber within the tool upper part; and wherein a vacuum sensor is operably connected to the control unit and the vacuum sensor is disposed between the dome-shaped die and a vacuum generator to generate a pressure profile during a sealing operation, the control unit being operable to detect a tear in the top film on the basis of the pressure profile.
 2. The tray sealer according to claim 1, wherein the dome-shaped die comprises a plurality of venting ducts.
 3. The tray sealer according to claim 1, wherein the dome-shaped die has a sealing surface.
 4. The tray sealer according to claim 3, wherein the dome-shaped die is movable between an upper position for deforming the top film and a lower position for sealing the top film onto a tray edge of at least one tray.
 5. The tray sealer according to claim 1, further comprising a seal disposed at a transition of the first channel from the dome-shaped die to the second channel of the tool upper part.
 6. A method of operating a tray sealer, wherein the tray sealer includes a control unit and a sealing station, the sealing station comprising a tool upper part, a clamping frame and a tool lower part, wherein the tool upper part receives therein a dome-shaped die for deforming a top film, wherein the dome-shaped die comprises at least a first channel, wherein the tool upper part comprises a second channel, wherein the dome-shaped die has an inner contact surface, and wherein the clamping frame is configured to clamp the top film in position on the tool upper part in a gas-tight manner so as to define a chamber within the tool upper part, the method comprising: measuring a negative pressure using a vacuum sensor disposed between the dome-shaped die and a vacuum generator; generating a pressure profile based upon the measured negative pressure; and detecting a tear in the film based upon the pressure profile using the control unit.
 7. The method according to claim 6, further comprising displaying a message using the control panel when a tear in the film is detected.
 8. The method according to claim 6, further comprising one of (a) not starting a sealing process or (b) discontinuing a sealing process when a tear in the film is detected using the control unit.
 9. The method according to claim 6, further comprising the steps of: supplying air to the upper tool part after a tear in the film is detected; advancing the top film in the conveying direction; and thermoforming a subsequent section of the top film into the dome-shaped die after the advancing the top film step for sealing the tray.
 10. The method according to claim 6, further comprising: detecting that the top film is in contact with the inner contact surface of the dome-shaped die using the pressure profile. 